1. Field of the Invention
This invention relates to a diamond pn junction diode and a method for fabrication thereof.
2. Description of the Prior Art
Diamond has superior physical and chemical characteristics as a wide-band gap semiconductor and can operate at temperatures as high as 1000xc2x0 C. as opposed to silicon (Si), which can only be used at temperatures below 200xc2x0 C. In the application of diamond, with its superior characteristics, to electronic devices, basically a p-type semiconductor and n-type semiconductor are formed as the foundation and then a diamond pn junction diode is formed.
However, particularly from the viewpoint of device application, technology must be developed that will control the electrical conductivity (p-type, n-type) using ion implantation and that will join the p-type semiconductor and n-type semiconductor, but compared to silicon (Si), almost no viable applications such as an ion implantation method have been realized.
This invention was proposed to address this problem and its purpose is to offer a diamond pn junction diode and its fabrication method to serve as a basis for allowing the application of diamond semiconductor as an electronic device by employing an ion implantation method.
To achieve the above objective, the diamond pn junction diode of this invention is fabricated by forming a p-type diamond thin-film layer on a substrate and a high-quality undoped diamond thin-film layer on this p-type diamond thin-film layer, and then making the above formed thin-film layer an n-type diamond thin-film layer by ion implantation of an impurity.
The above p-type diamond thin-film layer also includes a thin-film layer in which a high-quality undoped diamond thin-film layer is formed on a substrate and this formed diamond thin-film layer is doped with an impurity.
Further, the diamond pn junction diode of this invention comprises an n-type diamond thin-film layer formed on a substrate and a high-quality undoped diamond thin-film layer formed on this n-type diamond thin-film layer, which is then made a p-type diamond thin-film layer by ion implantation of an impurity on the formed thin-film layer.
The above n-type diamond thin-film layer also includes a thin-film layer in which a high-quality undoped diamond thin-film layer is formed on a substrate and this formed thin-film layer is doped with an impurity.
The above p-type thin-film layer includes a layer wherein the substrate on which it is formed is a p-type and a p-type diamond thin-film layer in which the hole density is lower than the hole density in the substrate.
Further, the above n-type thin-film layer includes a layer wherein the substrate on which it is formed is an n-type and an n-type diamond thin-film layer wherein the electron density is lower than the electron density of the substrate.
Further, the above high-quality undoped diamond thin-film layer includes a layer of sufficiently high quality that it emits intrinsic ultraviolet light at room temperature by any excitation method such as the electron injection one when the film thickness is at least 200 nm.
When the above p-type diamond thin-film layer surface and n-type diamond thin-film layer surface become the top layer in a lamination, that surface is made a graphite low-resistance layer by ion implantation and an electrode is formed on this graphite low-resistance layer.
The diamond pn junction diode fabrication method of this invention makes a diamond pn junction diode by forming a p-type diamond thin-film layer on the above substrate, forming a high-quality undoped diamond thin-film layer on the formed diamond thin-film layer, and making this formed diamond thin-film layer an n-type diamond thin-film layer by ion implantation of an impurity.
The diamond pn junction diode fabrication method of this invention makes a diamond pn junction diode by forming an n-type diamond thin-film layer on the above substrate, forming a high-quality undoped diamond thin-film layer on the formed diamond thin-film layer, and making this formed diamond thin-film layer a p-type diamond thin-film layer by ion implantation of an impurity.
In the above diamond pn junction diode fabrication method, the above high-quality undoped diamond thin-film layer includes a thin-film layer of sufficiently high quality to emit intrinsic ultraviolet light at room temperature by any excitation method such as the electron injection one when its film thickness is at least 200 nm.
As described above, by means of the diamond pn junction diode and its fabrication method of this invention, it is possible to reliably control the electrical conductivity of diamond by ion implantation, which had not been realized in most cases in the prior art, by ion implantation of an impurity on a high-quality undoped diamond thin-film layer, and since we were able to join diamond thin-film layers that demonstrate remarkable p-type and n-type characteristics through control of the electrical conductivity, it is possible to reliably fabricate diamond pn junction diodes which could not be realized in the prior art.